The proposed research will investigate the cognitive processes underlying the profile of language strengths and weaknesses seen in autism. Until recently, research in this area has focused on documenting the separate aspects of language that are impaired or intact in individuals with autism. As a result, we have an adequate description of the profile of language in autism, but we still do not have a clear understanding of why the profile exists. With this study, we will try to further clarify language functioning in autism by examining the role that two different cognitive deficits, namely general processing system limitations and theory of mind impairments, may play in determining the specific language difficulties observed. We will compare the performance of a group of individuals with autism to two control groups on three different tests of language processing (Word List Recall, Social Faux Pas, and Joke Comprehension). Thus, the groups to be studied will be (N-30 per group): adults with high-functioning autism; a clinical comparison group of individuals with Fragile X syndrome matched to the autism group on verbal mental age and chronological age; and a normally functioning control group matched on verbal mental age and gender. Based on previous research showing general processing limitations in autism, we predict that subjects with autism will show decrements in performance whenever significant general processing demands are imposed (e.g. having to draw an inference from a text passage and shift cognitive set). In addition, based upon research showing theory of mind impairments in autism, we also predict that theory of mind requirements will lead to autism-specific decrements in performance (e.g. deficits whenever a mental representation of an other mind is necessary). Further, we will test the relation between performance on these experimental tests of language function, and qualitative ratings of pragmatic abilities in naturalistic contexts, by examining the correlation between performance on these measures.